Two large reciprocal translocations characterized in the disease resistance-rich burmannica genetic group of Musa acuminata

Abstract

Background and Aims Banana cultivars are derived from hybridizations involving Musa acuminata subspecies. The latter diverged following geographical isolation in distinct South-east Asian continental regions and islands. Observation of chromosome pairing irregularities in meiosis of hybrids between these subspecies suggested the presence of large chromosomal structural variations. The aim of this study was to characterize such rearrangements. Methods Marker (single nucleotide polymorphism) segregation in a self-progeny of the ‘Calcutta 4’ accession and mate-pair sequencing were used to search for chromosomal rearrangements in comparison with the M. acuminata ssp. malaccensis genome reference sequence. Signature segment junctions of the revealed chromosome structures were identified and searched in whole-genome sequencing data from 123 wild and cultivated Musa accessions. Key Results Two large reciprocal translocations were characterized in the seedy banana M. acuminata ssp. burmannicoides ‘Calcutta 4’ accession. One consisted of an exchange of a 240 kb distal region of chromosome 2 with a 7.2 Mb distal region of chromosome 8. The other involved an exchange of a 20.8 Mb distal region of chromosome 1 with a 11.6 Mb distal region of chromosome 9. Both translocations were found only in wild accessions belonging to the burmannicoides/burmannica/siamea subspecies. Only two of the 87 cultivars analysed displayed the 2/8 translocation, while none displayed the 1/9 translocation. Conclusion Two large reciprocal translocations were identified that probably originated in the burmannica genetic group. Accurate characterization of these translocations should enhance the use of this disease resistance-rich burmannica group in breeding programmes.

Genome ancestry mosaics reveal multiple and cryptic contributors to cultivated banana

“…siamea accessions were clustered in one ancestral group and accessions from these subspecies had a homogenous local ancestry profile. This confirmed the idea of a single genetic group predicted by SSR and large structural variation analyses (Perrier et al , ; Dupouy et al , ) . The malaccensis subspecies is geographically close to ssp.…”

Chromosome painting in cultivated banana and their wild relatives (Musaspp.) reveals differences in chromosome structure

“…burmannicoides) was estimated to be 240 kb (Dupouy et al, 2019). The size of the translocated regions of chromosomes 1 and 9 was estimated to be 20.8 Mb and 11.6 Mb respectively (Dupouy et al, 2019). Using oligo painting, we did not detect the 240 kb distal region of chromosome 2 translocated to chromosome 8, and this may reflect the limitation in the sensitivity of whole chromosome arm oligo painting.…”

“…The authors estimated the size of translocated region of chromosome 8 to chromosome 2 to be 7.2 Mb, while the size of the distal region of chromosome 2, which was found translocated to chromosome 8 in wild diploid clone 'Calcutta 4' (ssp. burmannicoides) was estimated to be 240 kb (Dupouy et al, 2019). The size of the translocated regions of chromosomes 1 and 9 was estimated to be 20.8 Mb and 11.6 Mb respectively (Dupouy et al, 2019).…”

“…We cannot exclude differences in chromosome structure within individual subspecies. However, given the large genetic homogeneity of the six subspecies as clearly demonstrated by molecular markers (Carreel et al, 2002, Hřibová et al, 2011, Němečková et al, 2018, Dupouy et al, 2019, this does not seem probable. We observed a conserved genome structure in M. acuminata ssp.…”

“…siamea, which have similar phenotype and geographic distribution (Simmonds, 1962 share a translocation of a part of the long arm of chromosome 8 to the long arm of chromosome 2, and a reciprocal translocation between chromosomes 1 and 9. These translocations were identified recently by Dupouy et al (2019) after mapping mate-paired Illumina sequence reads to the reference genome of 'DH Pahang'.…”